SERVER-47695: Don't set lastOp for client backwards in terms of timestamp after rollback

(cherry picked from commit bd579c0d3f2583c2af7dcd98c7f6cfc55009b406)

1 files changed, 7 insertions, 4 deletions

diff --git a/src/mongo/db/repl/repl_client_info.cpp b/src/mongo/db/repl/repl_client_info.cpp
index 2538e7d16c5..21b6d0980ea 100644
--- a/src/mongo/db/repl/repl_client_info.cpp
+++ b/src/mongo/db/repl/repl_client_info.cpp
@@ -97,10 +97,13 @@ void ReplClientInfo::setLastOpToSystemLastOpTime(OperationContext* opCtx) {
             // above.
         }
 
-        // If the system optime has gone backwards, that must mean that there was a rollback.
-        // This is safe, but the last op for a Client should never go backwards, so just leave
-        // the last op for this Client as it was.
-        if (systemOpTime >= _lastOp) {
+        // If the system timestamp has gone backwards, that must mean that there was a rollback.
+        // If the system optime has a higher term but a lower timestamp than the client's lastOp, it
+        // means that this node's wallclock time was ahead of the current primary's before it rolled
+        // back. This is safe, but the timestamp of the last op for a Client should never go
+        // backwards, so just leave the last op for this Client as it was.
+        if (systemOpTime.getTerm() >= _lastOp.getTerm() &&
+            systemOpTime.getTimestamp() >= _lastOp.getTimestamp()) {
             _lastOp = systemOpTime;
         } else {
             LOGV2(21280,